Telecommunications racks are used to support telecommunications equipment on floors of office buildings that are designed to bear these loads. These racks also permit cables to be installed and maintained while the equipment is in place.
In North America and Europe, standards or criteria are set for allowable dimensions for equipment in the telecommunications industry. The North American standards are known as NEBS standards (Network Equipment Building system) and the European standards are set by ETSI (European Telecommunications Standards Institute). The NEBS standards vary for buildings in different geographic locations, and telecommunications equipment must meet these specifications in order to be installed in the particular buildings. In earthquake sensitive areas, the NEBS standards also address design criteria under critical loading situations.
The design criteria stipulate, among other things, the maximum deflection of the top of the rack under seismic loading conditions. To meet these criteria, the rack should be relatively stiff. One difficulty with these designs is that racks gain weight in order to meet this stiffness requirement. The effect of this increased stiffness is that the natural frequency of the rack, which is calculated by dividing the stiffness of the rack by its weight, is reduced. A low value of natural frequency is a disadvantage since this increases the likelihood of catastrophic failure under seismic loading conditions.
Telecommunications racks are typically constructed with members which are made of various alloys of aluminum or steel. Various techniques are used to make these members, such as roll forming or extrusion, and the members are either welded or bolted together. The members of these racks typically have flat and solid surfaces, which do not allow cables to pass through the members. Creating openings in these members for cabling is undesirable since the openings will weaken or reduce the stiffness of the rack.